vacuum or fuel pump?
New User
Joined: Mar 2007
Posts: 16
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The vacuum pump will occasionally run at start up if the reservoir level has been depleted due to a slow leak in the hublock or hvac system and you will hear it under the hood. The fuel pump will always run at start up for a few seconds and is down on the frame.
Most likely, you are hearing the fuel pump.
Most likely, you are hearing the fuel pump.
Posting Guru
Joined: Jul 2007
Posts: 1,233
Likes: 0
From: Las Vega$
the vacuum pump is quite a bit louder, and is usually the one you hear when you cycle the key on.
do this:
pop your hood and open your door. turn the key on from outside the vehicle and listen.
the fuel pump is mounted inside your left frame rail, pretty much directly under the driver seat.
the vacuum pump is mounted in the engine compartment on top of the passenger side fender liner.
do this:
pop your hood and open your door. turn the key on from outside the vehicle and listen.
the fuel pump is mounted inside your left frame rail, pretty much directly under the driver seat.
the vacuum pump is mounted in the engine compartment on top of the passenger side fender liner.
Elder User
Joined: Apr 2004
Posts: 797
Likes: 0
From: Wickenburg, AZ
It'll be the vacuum pump. When I flip the key on, it runs the vacuum pump for a bit, then tests the ABS pump, and by then it's usually ready to start.
You can pick up the fuel pump if you crouch down on the driver's side. You can hear the fuel pressurize in the filter bowl with the hood up, too. It's more noticeable when you swap out fuel filters.
You can pick up the fuel pump if you crouch down on the driver's side. You can hear the fuel pressurize in the filter bowl with the hood up, too. It's more noticeable when you swap out fuel filters.
Hotshot
Joined: Jul 2005
Posts: 13,834
Likes: 25
From: Middle Tn.
Correct me if I am wrong but the vacuum pump will operate even when the engine is running since diesels do not produce vacuum hence the hydro-boost brake system. On the 08's there will be an optional vacuum brake system and the engine drive accessories will include a vacuum pump for the brake system. Will not be available on dual alternator trucks.
Posting Guru
Joined: Jul 2007
Posts: 1,233
Likes: 0
From: Las Vega$
yes the vacuum pump operates even when the engine is running. correct the brakes use hydraboost from the power steering. the vacuum pump is there to power things like the front hub locks on 4wd , and the HVAC controls for heater/ac etc..
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Lead Driver
Joined: Sep 2006
Posts: 5,665
Likes: 164
From: Cartersville, Ga
On occasional startups the pump from under the hood is a lot louder than normal. It sounds like it is working twice as hard. Is that ok or is something getting ready to go out.
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Senior User
Joined: Jan 2004
Posts: 238
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From: Eastern PA
My Vacuum pump will not shut off. After I cycle the key and then start the truck it continues to run....is the pump bad or is there a leak? Also noticed that my A/C was very slow to go to recirculate on MAX A/C...
Postmaster
Joined: Dec 2003
Posts: 4,196
Likes: 10
From: Arizona
Originally Posted by Dieselman929
My Vacuum pump will not shut off. After I cycle the key and then start the truck it continues to run....is the pump bad or is there a leak? Also noticed that my A/C was very slow to go to recirculate on MAX A/C...